Enable AArch64 processor feature detection unconditionally (#4034)

std::arch::is_aarch64_feature_detected!() is now part of stable
Rust, so we can always use it.

Copyright (c) 2022, Arm Limited.

.github/workflows/main.yml

@@ -62,7 +62,7 @@ jobs:
         submodules: true
     - uses: ./.github/actions/install-rust
       with:
-        toolchain: nightly-2021-12-15
+        toolchain: nightly-2022-04-27
 
     # Build C API documentation
     - run: sudo apt-get update -y && sudo apt-get install -y libclang1-9 libclang-cpp9
@@ -178,7 +178,7 @@ jobs:
     # flags to rustc.
     - uses: ./.github/actions/install-rust
       with:
-        toolchain: nightly-2021-12-15
+        toolchain: nightly-2022-04-27
     - run: cargo install cargo-fuzz --vers "^0.11"
     # Install OCaml packages necessary for 'differential_spec' fuzz target.
     - run: sudo apt install -y ocaml-nox ocamlbuild ocaml-findlib libzarith-ocaml-dev

cranelift/native/src/lib.rs

@@ -105,8 +105,7 @@ pub fn builder_with_options(infer_native_flags: bool) -> Result<isa::Builder, &'
         }
     }
 
-    // `stdsimd` is necessary for std::is_aarch64_feature_detected!().
-    #[cfg(all(target_arch = "aarch64", feature = "stdsimd"))]
+    #[cfg(target_arch = "aarch64")]
     {
         use cranelift_codegen::settings::Configurable;
 
@@ -114,7 +113,7 @@ pub fn builder_with_options(infer_native_flags: bool) -> Result<isa::Builder, &'
             return Ok(isa_builder);
         }
 
-        if std::is_aarch64_feature_detected!("lse") {
+        if std::arch::is_aarch64_feature_detected!("lse") {
             isa_builder.enable("has_lse").unwrap();
         }
     }

crates/fuzzing/src/generators.rs

@@ -702,7 +702,7 @@ impl<'a> Arbitrary<'a> for CodegenSettings {
                         // print a warning and return an error because this fuzz
                         // input must be discarded.
                         #[cfg(target_arch = $arch)]
-                        if enable && !std::$test!($std) {
+                        if enable && !std::arch::$test!($std) {
                             log::warn!("want to enable clif `{}` but host doesn't support it",
                                 $clif);
                             return Err(arbitrary::Error::EmptyChoose)
@@ -752,6 +752,11 @@ impl<'a> Arbitrary<'a> for CodegenSettings {
                     std:"avx512vl" => clif:"has_avx512vl" ratio: 1 in 1000,
                     std:"avx512vbmi" => clif:"has_avx512vbmi" ratio: 1 in 1000,
                 },
+                "aarch64" => {
+                    test: is_aarch64_feature_detected,
+
+                    std: "lse" => clif: "has_lse",
+                },
             };
             return Ok(CodegenSettings::Target {
                 target: target_lexicon::Triple::host().to_string(),

crates/wasmtime/src/engine.rs

@@ -388,9 +388,23 @@ impl Engine {
                 ))
             }
         }
+
+        let enabled;
+
+        #[cfg(target_arch = "aarch64")]
+        {
+            enabled = match flag {
+                "has_lse" => Some(std::arch::is_aarch64_feature_detected!("lse")),
+                // fall through to the very bottom to indicate that support is
+                // not enabled to test whether this feature is enabled on the
+                // host.
+                _ => None,
+            };
+        }
+
         #[cfg(target_arch = "x86_64")]
         {
-            let enabled = match flag {
+            enabled = match flag {
                 "has_sse3" => Some(std::is_x86_feature_detected!("sse3")),
                 "has_ssse3" => Some(std::is_x86_feature_detected!("ssse3")),
                 "has_sse41" => Some(std::is_x86_feature_detected!("sse4.1")),
@@ -412,18 +426,25 @@ impl Engine {
                 // host.
                 _ => None,
             };
-            match enabled {
-                Some(true) => return Ok(()),
-                Some(false) => {
-                    return Err(format!(
-                        "compilation setting {:?} is enabled but not available on the host",
-                        flag
-                    ))
-                }
-                // fall through
-                None => {}
+        }
+
+        #[cfg(not(any(target_arch = "aarch64", target_arch = "x86_64")))]
+        {
+            enabled = None;
+        }
+
+        match enabled {
+            Some(true) => return Ok(()),
+            Some(false) => {
+                return Err(format!(
+                    "compilation setting {:?} is enabled, but not available on the host",
+                    flag
+                ))
             }
+            // fall through
+            None => {}
         }
+
         Err(format!(
             "cannot test if target-specific flag {:?} is available at runtime",
             flag